1. Field of the Invention
The present invention relates to a liquid droplet discharge head, a liquid droplet discharge device and an image forming apparatus, and more particularly, to a structure of a liquid droplet discharge head which are suitable for use in an image forming apparatus, such as an inkjet recording apparatus which forms images on a recording medium by discharging liquid droplets from nozzles, and to a technology for determining discharge errors in the liquid droplet discharge head.
2. Description of the Related Art
An inkjet recording apparatus is an apparatus for forming images by means of ink dots, by causing ink to be discharged from a recording head comprising nozzles for discharging ink, in accordance with a print signal, thereby causing ink droplets to land on a recording medium, such as recording paper, or the like, while moving the recording medium relatively with respect to the recording head. In an apparatus of this kind, if an air bubble is present in the nozzles of the flow channel in the vicinity of the nozzles, then a problem arises in that the ink cannot be discharged normally. Therefore, technologies have been proposed for judging the presence or absence of air bubbles through optical observation of the flow channels inside the head.
Japanese Utility Model Application Publication No. 1-83546 discloses technology for determining air bubbles inside the flow channels of the head by means of an optical device. Japanese Patent Application Publication No. 7-232440 proposes the use of infrared light as the wavelength of the determination light source. Japanese Patent Application Publication No. 2000-15841 proposes that a portion of the flow channel be constituted by a transparent member, the wavelength of the determination light source being varied in accordance with the type (color) of ink, and also proposes that the satisfactory or unsatisfactory discharge status be judged by processing a determination image obtained by scanning the determination system in the direction in which nozzles are arranged.
However, the technologies proposed in the prior art are applicable only to heads having a relatively simple structure, and are not compatible, for example, with heads having a complicated structure, such as those where the internal flow channels (including the liquid chambers) are arranged three-dimensionally in an overlapping fashion, by means of a layered structure. For example, a head composition has been devised in which the flow channel sections, such as the pressure chambers and common flow channels, are arranged in a layered structure, in order to achieve higher nozzle density. If the technologies proposed in the prior art are applied to a head of this kind, then although the liquid chambers in the vicinity of the determination system can be observed, those liquid chambers which are distant from the determination system cannot be observed because they are shielded from view by the liquid chambers in front of them. Even supposing that a transparent material is used to compose all of the members forming the flow channels in the head, then while the locations of air bubbles can be specified in the planar direction captured by the optical sensor, it is difficult to identify their location in the depth direction, namely, to identify which layer of liquid chambers, of the plurality of liquid chambers arranged in different layers, the air bubbles are located in.